A drug for the treatment of high blood phosphate levels is offering relief for dialysis patients. 

Fosrenol, or lanthanum carbonate, has been developed by the speciality chemicals company Johnson Matthey, UK, and its spin-off company AnorMED, based in Canada, in collaboration with the pharmaceutical company Shire, UK. The drug has been in use in the US since January 2005 and is proving to be a 'successful lanthanide-based drug,' said Simon Fricker of AnorMED.

Hyperphosphataemia is an abnormally raised level of blood phosphate, often associated with kidney disease. In the US around a quarter of a million people suffer from this condition. Under normal circumstances, the intestine, liver and kidneys maintain a net phosphate balance of zero, but in patients with kidney failure, high levels of phosphate can lead to severe bone-joint malformations and cardiovascular problems. The latter are the major cause of death for dialysis patients.

One common treatment for high blood phosphate uses compounds called phosphate binders; in the gut these prevent phosphate uptake from the diet. 'The ideal phosphate binder should have low solubility and little or no systemic adsorption. It should be non-toxic and available in a palatable oral dosage form,' said Fricker. Aluminium and calcium based phosphate binders can cause problems due to metal ion absorption, he said. Fosrenol avoids the adverse effects associated with earlier drugs because it cannot cross the gut lining and so is not transmitted to the rest of the body.

Since the early twentieth century, lanthanides have found various applications in the treatment of nausea, tuberculosis and the hardening of arteries. In recent years they have fallen out of favour and most new drug development routes have been unsuccessful. 'Thirty years ago, chelation of toxic metals was the nearest inorganic chemistry came to [a clinical use],' said Robert Bulman of the Health Protection Agency in the UK. 'Fosrenol has become an effective therapy for hyperphosphataemia in renal patients and it is likely that the [lanthanides' therapeutic] role will increase.'

Michael J Spencelayh